Self-locking folding box construction



Sept- 1955 F. E. HELMICK SELF-LOCKING FOLDING BOX CONSTRUCTION 2Sheets-Sheet 1 Filed April 5, 1952 INVENTOR. Fr'eaer/ck E A's/mick Sept.27, 1955 F. E. HELMICZK 2,718,999

SELF-LOCKING FOLDING BOX CONSTRUCTION Filed April 5, 1952 2 Sheets-Sheet2 INVENTOR. Frederick E. Helm/ck 4M ATTORNEY United States PatentSELF-LOCKING FOLDING BOX CONSTRUCTION Frederick E. Helmick, Belmont,Califi, assignor, by mesue assignments, to Balj'ak Corporation,Wilmington, DeL, a corporation of Delaware Application April 5, 1952',Serial No. 280,7 9-1 4 Claims. (Cl. 229-35),

This invention relates to improvements. in cartons, boxes, trays, orother structures: made from blanks of cardboard, paperboard. or othersuitable, fold'able sheet material hereinafter collectively referred toas boxes,

folding boxes.

More particularly, the invention applies-to gluel'esslyassembled foldingboxes in which the box corners arelocked by means of a lock flaparticulated to one wall panel and inserted into a cut in another wallpanel which extends from the body of the other wall panel into a topflap articulated to the other wall panel along-a top: fold line.

Box corner constructions of this general type are favored for thepackaging of frozen foods, and the corner lock is quite secure if thebox is closed.

The folding of the top flap tends to close the locking cut tightly,since in the locked and closed box the locking cut extends from onepanel into another panel lying at an angle thereto, and the lock flapwhich extends through the cut is locked in position firstly byfrictional engage-- ment at the tightly closed cut, and secondly alocking tip on the lock flap is bent into an angular position withrespect to the remainder of the lock flap by the folding of the topflap, and thus prevents the lock flap from being withdrawn from the cut.

Locks of the aforementioned type are satisfactory and secure as long asthe top fla-pssometimes also referred to as dust flaps in the box artarefolded. However, all previous corner constructions of this type, as faras I' am aware, have the disadvantage of being quite unreliable prior tothe folding of the top flaps, particularly during the period of fillingof the box with contents. In the case of frozen food boxes which arefilled on automatic machinery, and especially in the case of boxes intowhich the contents are tightly packed, accidental opening of a cornerlock amounts to a serious disturbance of the packaging procedure, sincethe box" in question must be removed f'rom the automatic machine.Frequently, the failing box jams before itsremoval, or otherwisedisturbs the functioning of the machine. This requires temporarystopping of a whole line of machinery which generally comprises a boxforming machine, a box filling machine, a box closing machine, andfinally a box wrapping machine, allinterconnected by a common drive forsynchronized operation.

The present invention provides an improvedcornerconstruction of theaforementioned type which is secure against accidental opening of thebox corner from the time the box leaves the box forming machine. Moreparticularly, the improved lock does not depend on the fold-- valuablein frozen food boxesdue to the inevitable-expamsion ofthe boxcontentsduring freezing-.

The reliability of the improved lock makesthe improved cornerconstruction particularly suited for: handling on automatic filling andclosing machinery, and it eliminates the previously experienceddisturbances due to accidental opening of the box corners.

These and other features, objects and advantages-of the invention willappear more fully from the detailed description which follows,accompanied by drawings showing, for the purpose of illustration, apreferred embodiment of the invention.

The invention also consists in new and improved details of constructionhereinafter set forth and claimed.

Although the characteristic features of the invention which are believedto be novel will be particularly pointed out in the claims appendedhereto, the invention itself, and the manner in which it may be carriedout, may be better understood by referring to the following descriptiontaken in connection with the accompanying drawings forming a part of itin which:

Fig. 1 is a plan view of a flat box blank embodying the invention, theinside surface of the blank facing the observer;

Fig. 2 is a perspective View of the box blank of Fig. l in the processof assembly, but prior to the completion of the corner locks;

Fig. 3' is: a perspective view of the box shown in Fig. 2 aftercompletion of the corner locks, but prior to folding of the top flaps,the box being ready for filling;

Fig. 4 is a perspective view of the box of Fig. 3 with thecorners lockedand secured by folding of the top flaps; and

Fig. 5 is a perspective view of the inside. of the view being taken inthe direction of arrow 5 in Fig. 4.

in the following description and in the claims, various. structuraldetails will be identified by specific names for convenience. The names,however, are intended to be as generic. in their application as the artwill permit. Corresponding reference characters refer to corresponding,parts in the several figures, of the drawings.

In the drawings accompanying, and forming part of; this specification,certain specific disclosure of the invention is; made for the purpose ofexplanation of broader aspects of the invention, but it is understoodthat the details may be modified in various respects without departure'from the: principles of, the invention and that the invention may beapplied to other structures than the one shown.

The blank A. shown in Figure 1 may be cut and scored, inmultiple, from alarge sheet or roll of paperboard or other suitable foldablematerial onan automatic cutting and? scoring machine. Only one sideof the blankneed be decoratively finished or imprinted, since only one side of theblank is presented as the outside of the finished, box. If the box is tobe: used for the packaging of frozen foods, waxed, or otherwisemoisture-proofed stock is'used.

The blank. A is sub-divided by several scored. fold lines toprovide amain or bottom panel 11 to which side wall panels; 12 and 13 arearticulated along side fold lines 14 and 15. Front and back panels 16and 17 are ar-ticu latedto. the bottom panel 11 along foldlines 18 and-19, respectively.

Lock flaps 20, 21, 22 and 23 are articulated to. the front and backpanels 16 and 17, respectively, along side fold.

lines 24, 25, 26 and 27, respectively. These side foldlines, are eitheraligned with, or slightly offset with respect to, thefold lines 14 and15 to compensate for the thickness, of the board, in a conventionalmanner. Corner fl'aps 28, 29, 3t and 31 are articulated to the side wallpanels 12' and 13, respectively, along side fold lines 32, 33, 34 and35-.

Top flaps 36 and 37 are articulated to the side wall panels 12 and 13-along top fold lines 38 and 39, respect-ively.

A-cover panel 40 is articulated to the back panel: 11

.2 along a fold line 4-1 and a cover flap 42 extends hingedly from thecover panel along a fold line 43. The cover flap 42 has a two-prongedlock tab 44- of more or less conventional configuration for engagementwith a tab locking cut 45 in the front panel 16.

The improved corner locks of the box blank comprise internal cuts ofbent outline in the side wall panels and in the associated top flapswhich engage lock tips on the respective lock flaps. In the illustratedembodiment the construction of all four box corners is alike and it willtherefore be suflicient to describe one of the four cuts 46, 47, 48 and49, and one of the associated lock tips 50, 51, 52 and 53.

The internal cut 47 is of bent outline and comprises a first portion 54within the body of the side wall panel 12. The first portion extends tothe top fold line and thence the cut continues into the body of the topflap 36, the continuing portion of the cut being numbered 55. It will benoted that the cut portion 55 extends at an angle with regard to theportion 54, and also forms an angle on with regard to the top fold line38. An end portion 56 of the cut extends at an angle with respect toportion 55 and is preferably substantially parallel to the top fold line355. The distance, or mean distance, of the end portion 56 from the topfold line 38 is indicated as h.

The internal cut 47 forms an internal tongue 53 in the side wall 12 andin the top flap 36. This internal tongue extends towards the adjacentbox corner and is relatively easily deflected with regard to theremainder of the blank, as long as the wall panel 12 and its flap 36 liein the same plane. It is evident, however, that this tongue will becomerigid and inflexible when the flap 36 is bent with respect to the wallpanel 12, as will later appear.

The internal tongues formed by internal cuts 46, 48 and 49 are numbered57, 59 and 69, respectively.

A lock tip 51 extends from the lock flap 22 for engagement with theinternal cut 47. The lock tip may be a part of the panel proper of thelock flap 22, but is preferably articulated thereto along a tip foldline 61. The height of the tip above the fold line 61, or above thecontinuing edge 62 of the lock flap 22 is indicated as H and is greaterthan the distance h previously mentioned. These dimensions are based onthe condition that the height of the side wall panels 12 and 13 issubstantially equal to the height of the front and back wall panels 16and 17, except for allowances for board thickness to facilitate folding.

The size relation may also be expressed in terms of distance from therespective fold lines which define the main panel 11. If so considered,the distance of the point of the lock tip 51 from the fold line 19, orits con tinuation, is greater than the distance of the end portion 56 ofthe internal cut from the fold line 14. The reasons for these particulardimensions will become apparent from a consideration of the assemblyprocedure.

The lock tips 50, 52 and 53 may be articulated to their respective flaps20, 21 and 23 along fold lines 63, 64 and 65, and the dimension of thesetips with regard to their respective cuts 46, 48 and 49 is the same aspreviously described in connection with the tip 51.

The formation of a box from the blank A may proceed as follows:

The corner flaps 28, 29, 3t} and 31 are first folded relatively to theside wall panels 12 and 13 into substantially upright position. The sidewall panels 12 and 13 are then folded upright with respect to the bottompanel 11 along fold lines 14 and 15. Substantially simultaneously, orshortly thereafter, the front and back panels 16 and 17 are foldedupright with respect to the bottom panel 11 along fold lines 18 and 19,and the lock flaps 20, 21, 22 and 23 are folded into a positionsubstantially parallel with the folded side wall panels 12 and 13. Theinternal tongues 57, 58, 59 and 60 are flexed towards the outside,causing the cuts to open so that the lock flaps 20, 21, 22 and 23 mayenter between the outside surface of the side wall panels and the insidesurface of the flexed tongues.

The resulting box structure is shown in Fig. 2. It will be noted thatthe four box corners are formed, but that they are not completely lockedsince the lock tips still lie on the outside of the respective topflaps. This is seen particularly well at 52 and 53.

As the next operation, the lock tips are pulled to the inside of thebox. This is done by grasping either the lock tip at its base or bygrasping the respective lock flap below the base of the lock tip andpulling it to the inside of the box until the lock tip snaps past theend portion 56 of the internal cut.

This operation is preferably performed by automatic machinery basicallyconsisting of a plunger which forces the flat blank through acorrespondingly shaped die. During the passage of the blank through thedie the internal tongues are flexed outwardly, and the same mechanismwhich performs the flexing then grasps the lock flap or the lock tipwhich slides under it and pulls the tip towards the inside of the box. Apreferred form of apparatus for this purpose is disclosed in the patentof John Pagendarm, No. 2,580,189, of December 25, 1951.

Fig. 3 illustrates the box with the corners locked, in the condition inwhich the box is discharged from the box forming mechanism disclosed inthe Pagendarm patent. The box is now ready for filling. Its corners willnot unlock, even if contents are packed in the box body with a certainamount of compression. The security of the lock is due to the fact thatthe lock tips extend beyond the confines of the internal cuts and thuscannot be withdrawn from the cuts without tearing of the board. Thecaliper of the board, as well as the grade of the board, is, of course,selected to withstand the stress to which the box is subjected duringthe normal handling by the box machinery, particularly by the fillingmachine.

The corner flaps 28, 29, 30 and 31 rest firmly against the adjacentfront and back panels. They seal the corners sufficiently tight topermit A of water to stand in the box for hours without leaking.

After the box is filled, the top flaps 36 and 37 are folded into aposition substantially parallel to the bottom panel 11 and the box coveris then closed and locked. Folding of the top flaps 36 and 37 withrespect to the side walls 12 and 13 transforms the previously flatinternal tongues into three-dimensional structures of angularcross-sections. In this process the portions of the internal tonguestend to return into the plane of the panels from which they were cut anda pinching action results at the point of entry of the lock flaps 20,21, 22 and 23 into the respective cuts.

In addition, the lock tips 50, 51, 52 and 53 are bent at right angleswith respect to the lock flaps from which they extend. This is shown onan enlarged scale in the perspective Fig. 5 in which the lock tip 51 isshown bent along the crease line 61 with respect to the lock flap 22.The lock tip 51 underlies the top flap 36, and it is evident that evensubstantial pressure against the back wall panel 17 will not cause thetip 51 to dislodge from its proper position. If subsequently the box isopened, and the top flaps are folded upward into substantially the sameplane as the side walls 12 and 13, the lock is still secure, since thetips will either remain in their bent position or, even if folded fiatwith the respective lock flap, they will still prevent unlocking of thebox corner since the height H is greater than the available space hthrough which they would have to slip out.

The invention thus provides an improved corner construction of greatstrength which eliminates the difiiculties previously experienced withcorner locks which tended to open prior to the folding of the top flaps.

What is claimed is:

1. A glueless corner construction for folding boxes fold line, saidfirst wall panel having an internal cut of bent outline thereinextending across said top fold line and forming a tongue from the stockof said first wall panel and said flap, said tongue pointing towards thebox corner; a lock flap articulated to the side edge of said second Wallpanel and folded into a position parallel with said first wall panel,said lock flap extending through said internal cut into a positionpartially inside said one wall panel, said lock flap having a tipthereon bordered by a locking edge engaging said out in the top flap incorner locking position, the distance from said top fold line to saidtip being greater than the distance from the top fold line to the end ofthe cut in said top flap, said tip being forceable against theresistance of the stock from which it is formed from a position outsidesaid top flap through said out into a position inside said top flap,thereby providing a secure lock even before folding of said top flap.

2. A glueless corner construction for folding boxes comprising, a mainpanel, a first wall panel articulated to the main panel along a firstfold line; a second wall panel articulated to the main panel along asecond fold line intersecting said first fold line at an angle, saidpanels being folded about said fold lines with respect to one anotherinto a position in whichthey form a box corner, a top flap articulatedto said first wall panel along a top fold line substantially parallel tosaid first fold line, said first wall panel having an internal cut ofbent outline therein extending across said top fold line at an acuteangle and into said top flap, the end portion of the out within said topflap being substantially parallel to said top fold line, said internalcut forming a tongue from the stock of both said first wall panel andsaid flap, said tongue pointing towards the box corner; a lock flaparticulated to the side edge of said second wall panel and folded into aposition parallel with said first wall panel, said lock flap extendingthrough said internal cut into a position partially inside said one wallpanel, said lock flap having a tip thereon bordered by a locking edgeengaging said cut in the top flap in corner locking position, thedistance from said top fold line to said tip being greater than thedistance from said top fold line to the said parallel cut portion, saidtip being forceable against the resistance of the stock from which it isformed from a position outside said top flap through said cut into aposition inside said top flap, thereby providing a secure lock evenbefore folding of said top flap.

3. A glueless corner construction for folding boxes comprising, a mainpanel, a first wall panel articulated to the main panel along a firstfold line; a second wall panel articulated to the main panel along asecond fold line intersecting said first fold line at an angle, saidpanels being foldable about said fold lines with respect to one anotherinto a position in which they form a box corner, a top flap articulatedto said first wall panel along a top fold line substantially parallel tosaid first fold line, said first wall panel having an internal cut ofbent outline therein extending across said top fold line and forming atongue from the stock of said first wall panel and said flap, saidtongue pointing towards the box corner; a lock flap articulated to theside edge of said second wall panel and foldable into a positionparallel with said one wall panel, said lock flap being insertablethrough said internal cut into a position partially inside said firstwall panel; and a lock tip articulated to said lock flap along a tipfold line substantially parallel to said second fold line and insubstantial registry with said top fold line when the panels are incorner forming position, the distance from said tip fold line to the endof the tip being greater than the distance from the top fold line to theend of the cut in the top flap, said tip being forceable against theresistance of the stock from which it is formed from a position outsidesaid top flap through said out into a position inside said top flap,thereby providing a secure lock of the corner even before folding of thetop flap and of the tip about their respective fold lines.

4. A glueless corner construction for folding boxes comprising, a mainpanel, a first wall panel articulated to the main panel along a firstfold line; a second wall panel articulated to the main panel along asecond fold line intersecting said first fold line at an angle, saidpanels being foldable about said fold lines with respect to one anotherinto a position in which they form a box corner, a top flap articulatedto said first wall panel along a top fold line substantially parallel tosaid first fold line, said first wall panel having an internal cut ofbent outline therein extending across said top fold line at an acuteangle and into said top flap, the end portion of the out within said topflap being substantially parallel to said top fold line, said internalcut forming a tongue from the stock of both said first wall panel andsaid flap, said tongue pointing towards the box corner; a lock flaparticulated to the side edge of said second wall panel and foldable intoa position parallel with said first wall panel, said lock flap beinginsertable through said internal cut into a position partially insidesaid one wall panel, and a lock tip articulated to said lock flap alonga tip fold line substantially parallel to said second fold line and insubstantial registry with said top fold line when the panels are incorner forming position, the distance from said tip fold line to the endof the tip being greater than the distance from the top fold line tosaid parallel cut portion, said tip being forceable against theresistance of the stock from which it is formed from a position outsidesaid top flap through said cut into a position inside said top flap,thereby providing a secure lock of the corner even before folding of thetop flap and of the tip about their respective fold lines.

References Cited in the file of this patent UNITED STATES PATENTS Re.12,217 Webb May 3, 1904 1,592,374 Lytle July 13, 1926 2,536,384 MellerJan. 2, 1951 2,553,870 Samsing May 22, 1951 2,617,580 Meller Nov. 11,1952 FOREIGN PATENTS 555,273 France Mar. 19, 1923

